Phase transformation in La(CoxNi5-x)-H systems (x = 2, 3, 5) studied by in situ X-ray diffraction

Yumiko Nakamura, Takahiro Nomiyama, Etsuo Akiba

Research output: Contribution to journalArticle

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Abstract

The phase transformation in the La(CoxNi5-x)-H systems (x = 2, 3, 5) were investigated using in situ X-ray diffraction (XRD). La(CoxNi5-x) (x = 2, 3) formed α, β, γ and δ hydride phases with increasing hydrogen content while LaCo 5 formed only α, β and γ hydride phases. The metal lattice of each phase is hexagonal in P6/mmm symmetry (α), orthorhombic in Cmmm symmetry (β) and orthorhombic in Im2m symmetry (γ), commonly observed for x = 2, 3, 5. The δ phase observed for x = 2, 3 has a hexagonal structure with P6/mmm symmetry, which was characterized for the first time in this study. The lattice expansion accompanied by the phase transformation was anisotropic for Co-rich compositions (x ≥ 2) compared with Ni-rich compositions (x = 0, 1). The lattice parameters changed with increasing hydrogen solution in the γ and δ single-phase regions for x = 2 and 3. Anisotropic lattice strain related with dense dislocations was not introduced through formation of any hydride phases. The isotropic strain increased upon formation of the δ phase but disappeared in subsequent phase transformation.

Original languageEnglish
Pages (from-to)54-62
Number of pages9
JournalJournal of Alloys and Compounds
Volume413
Issue number1-2
DOIs
Publication statusPublished - Mar 9 2006

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Hydrides
Phase transitions
X ray diffraction
Hydrogen
Chemical analysis
Lattice constants
Metals

All Science Journal Classification (ASJC) codes

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

Cite this

Phase transformation in La(CoxNi5-x)-H systems (x = 2, 3, 5) studied by in situ X-ray diffraction. / Nakamura, Yumiko; Nomiyama, Takahiro; Akiba, Etsuo.

In: Journal of Alloys and Compounds, Vol. 413, No. 1-2, 09.03.2006, p. 54-62.

Research output: Contribution to journalArticle

Nakamura, Yumiko ; Nomiyama, Takahiro ; Akiba, Etsuo. / Phase transformation in La(CoxNi5-x)-H systems (x = 2, 3, 5) studied by in situ X-ray diffraction. In: Journal of Alloys and Compounds. 2006 ; Vol. 413, No. 1-2. pp. 54-62.
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